An image forming apparatus such as a copying machine or a printer according to a related art includes a sheet feeding device that feeds a sheet, and as the sheet feeding device, there is a friction feed system in which a topmost sheet is separated and fed from a cassette on which a sheet bundle is loaded using frictional force of a rubber roller or the like. In the sheet feeding device of the friction feed system, the topmost sheet is fed by the rubber roller rotating while pressing the sheet bundle. Here, when a sheet is fed, multi-sheet feeding in which a plurality of sheets are conveyed by friction between sheets may occur. On the other hand, conveyance resistance works on the remaining sheets excluding the topmost sheet through a separating pad or a retard roller, and thus only the topmost sheet is fed to an image forming portion.
Meanwhile, in the sheet feeding device of the friction separation system, since the rubber roller feeds a sheet while applying great pressure to the sheet, noise generated by sliding friction between sheets or between the sheet and the rubber roller is problematic. In addition, when the multi-sheet feeding caused by the separating pad or the retard roller is prevented, sliding fricative between sheets is greatly generated. Further, since the separating pad or the retard roller serves as conveyance resistance of the topmost sheet even when the multi-sheet feeding does not occur, a sound is generated by stick slip between the separating pad or the retard roller and the sheet.
In this regard, as a technique of solving the problem, there is a sheet feeding device configured to separate and feed a sheet while adsorbing the sheet using electrostatic adsorption force, specifically, by an electric field formed on a belt surface (see Patent Literatures 1, 2, and 3). In the sheet feeding device of the electrostatic adsorption separation system, since it is possible to convey the topmost sheet as if the topmost sheet is peeled off from the sheet bundle, it is possible to significantly reduce noise generated in a feeding portion.